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Improve division of labor between execParallel.c and nodeGather[Merge].c.

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Move the responsibility for creating/destroying TupleQueueReaders into
execParallel.c, to avoid duplicative coding in nodeGather.c and
nodeGatherMerge.c.  Also, instead of having DestroyTupleQueueReader do
shm_mq_detach, do it in the caller (which is now only ExecParallelFinish).
This means execParallel.c does both the attaching and detaching of the
tuple-queue-reader shm_mqs, which seems less weird than the previous
arrangement.

These changes also eliminate a vestigial memory leak (of the pei->tqueue
array).  It's now demonstrable that rescans of Gather or GatherMerge don't
leak memory.

Discussion: https://postgr.es/m/8670.1504192177@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2017-09-01 17:38:54 -04:00
parent c039ba0716
commit 51daa7bdb3
5 changed files with 119 additions and 89 deletions
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18
src/include/executor/execParallel.h
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@@ -23,17 +23,21 @@ typedef struct SharedExecutorInstrumentation SharedExecutorInstrumentation;
typedef struct ParallelExecutorInfo
{
PlanState *planstate;
ParallelContext *pcxt;
BufferUsage *buffer_usage;
SharedExecutorInstrumentation *instrumentation;
shm_mq_handle **tqueue;
dsa_area *area;
bool finished;
PlanState *planstate; /* plan subtree we're running in parallel */
ParallelContext *pcxt; /* parallel context we're using */
BufferUsage *buffer_usage; /* points to bufusage area in DSM */
SharedExecutorInstrumentation *instrumentation; /* optional */
dsa_area *area; /* points to DSA area in DSM */
bool finished; /* set true by ExecParallelFinish */
/* These two arrays have pcxt->nworkers_launched entries: */
shm_mq_handle **tqueue; /* tuple queues for worker output */
struct TupleQueueReader **reader; /* tuple reader/writer support */
} ParallelExecutorInfo;
extern ParallelExecutorInfo *ExecInitParallelPlan(PlanState *planstate,
EState *estate, int nworkers, int64 tuples_needed);
extern void ExecParallelCreateReaders(ParallelExecutorInfo *pei,
TupleDesc tupDesc);
extern void ExecParallelFinish(ParallelExecutorInfo *pei);
extern void ExecParallelCleanup(ParallelExecutorInfo *pei);
extern void ExecParallelReinitialize(PlanState *planstate,